using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;

namespace WindowsGame4 {
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        Model terrain;

        Vector3 cameraPosition;
        Vector3 cameraDirection;
        Vector3 cameraUp;
        Matrix projection;
        Matrix view;

        Vector2 mousePosition;

        public Game1() {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize() {
            // TODO: Add your initialization logic here

            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent() {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            terrain = Content.Load<Model>("terrain");
            projection = Matrix.CreatePerspectiveFieldOfView(
                MathHelper.PiOver4, graphics.GraphicsDevice.Viewport.AspectRatio,
                1, 10000);

            cameraPosition = Vector3.Zero;
            cameraDirection = Vector3.Forward;
            cameraUp = Vector3.Up;

            MouseState mouse = Mouse.GetState();
            mousePosition = new Vector2(mouse.X, mouse.Y);
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent() {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime) {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            UpdateCamera(gameTime);

            base.Update(gameTime);
        }

        public void UpdateCamera(GameTime gameTime) {
            MouseState mouse = Mouse.GetState();
            Vector2 movedMousePosition = new Vector2(mouse.X, mouse.Y);
            float time = (float) gameTime.ElapsedGameTime.TotalSeconds;
            Vector2 rotationAmount = movedMousePosition - mousePosition;
            rotationAmount *= 0.01f;

            Vector3 cameraRight = Vector3.Cross(cameraDirection, cameraUp);

            Matrix yawMatrix =
                Matrix.CreateFromAxisAngle(cameraUp, rotationAmount.X);
            Matrix pitchMatrix =
                Matrix.CreateFromAxisAngle(cameraRight, rotationAmount.Y);
            Vector3 tiltedDirection = 
                Vector3.TransformNormal(cameraDirection, pitchMatrix * yawMatrix);
            tiltedDirection.Normalize();

            mousePosition = movedMousePosition;
            cameraDirection = tiltedDirection;

            Matrix.CreateWorld(ref cameraPosition, ref cameraDirection,
                ref cameraUp, out view);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime) {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            DrawModel(terrain, Matrix.Identity);
            // TODO: Add your drawing code here

            base.Draw(gameTime);
        }
        public void DrawModel(Model model, Matrix world) {
            foreach (ModelMesh mesh in model.Meshes) {
                foreach (BasicEffect effect in mesh.Effects) {
                    effect.World = world;
                    effect.View = view;
                    effect.Projection = projection;

                    effect.EnableDefaultLighting();

                    // Set the specular lighting to match the sky color.
                    effect.SpecularColor = new Vector3(0.6f, 0.4f, 0.2f);
                    effect.SpecularPower = 8;

                    // Set the fog to match the distant mountains
                    // that are drawn into the sky texture.
                    effect.FogEnabled = true;
                    effect.FogColor = new Vector3(0.15f);
                    effect.FogStart = 100;
                    effect.FogEnd = 320;
                }

                mesh.Draw();
            }
        }
    }
}
